Levers: 1st, 2nd, and 3rd Class Quiz

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Questions and Answers

What is a first class lever?

The fulcrum is at one end.

It has no mechanical advantage.

The load is between the fulcrum and the effort force.

The fulcrum is in the middle between the effort force and the resistance arm. (correct)

Define a lever.

A beam on a fulcrum that allows smaller force to move more weight.

Give examples of first class levers.

Scissors, can opener.

What is a second class lever?

The load is between the fulcrum and the effort force. Signup and view all the answers

Provide examples of second class levers.

Nut cracker, wheelbarrow. Signup and view all the answers

Calculate the mechanical advantage (MA) where LE=30 cm and LR=10 cm.

MA=3 Signup and view all the answers

What is the mechanical advantage formula?

MA= LE/LR Signup and view all the answers

Describe a third class lever.

Force is between the fulcrum and the load, with no mechanical advantage. Signup and view all the answers

Give examples of third class levers.

Bat, broom. Signup and view all the answers

Calculate the mechanical advantage (MA) where LR=80 cm and LE=20 cm.

MA=0.25 Signup and view all the answers

What is the formula for torque?

T= F x L Signup and view all the answers

Define torque.

Moment of force, or rotational force. Signup and view all the answers

What is the torque produced when a mechanic pulls on a 6-inch wrench with a force of 100 lbs?

600 in-lb Signup and view all the answers

What is the law of moments formula?

ME= FE x LE Signup and view all the answers

Calculate effort moments (ME) if the effort arm length (LE) is 153.5 in and the effort force (FE) is 63.5 lbs.

ME= 9748.25 in-lbs Signup and view all the answers

Determine the torque for a lever with a distance of 11.8 in and a force of 68.3 lbs-f.

805.94 in-lb Signup and view all the answers

What is a fulcrum?

The fixed point around which a lever pivots. Signup and view all the answers

What is the effort force?

Effort arm. Signup and view all the answers

What is the resistance force?

Resistance arm. Signup and view all the answers

If you change the _____, then the torque changes.

distance Signup and view all the answers

Study Notes

Levers Overview

Levers consist of a beam resting on a fulcrum, allowing a smaller force to lift a larger weight.
There are three classes of levers, each defined by the position of the fulcrum, effort, and load.

First Class Lever

The fulcrum is positioned between the effort force and the resistance arm.
Examples include scissors and can openers.

Second Class Lever

The load is positioned between the fulcrum and the effort force.
Examples include nut crackers and wheelbarrows.
Mechanical Advantage (MA) can be calculated using the formula: MA = LE/LR, where LE = Load Effort, LR = Load Resistance.
Example problem: If LE = 30 cm and LR = 10 cm, MA = 3.

Third Class Lever

The effort force is located between the fulcrum and the load, resulting in no mechanical advantage.
Examples include bats and brooms.
Example problem: If LR = 80 cm and LE = 20 cm, MA = 20/80 = 0.25.

Torque

Defined as "Moment of Force," it refers to the rotational force applied around a pivot point.
Formula for torque: T = F x L, where T is torque (in-lbs), F is force (lbs-f), and L is distance (in).
Example problem: A mechanic pulling on a 6-inch wrench with a force of 100 lbs results in T = 6 * 100 = 600 in-lbs.

Law of Moments

The relationship is given by the formula: ME = FE x LE.
ME = Effort Moments (in-lbs), FE = Effort Force (lbs), LE = Effort Arm Length (in).
Example problem: For a first class lever with LE = 153.5 in and FE = 63.5 lbs, ME = 153.5 x 63.5.

Key Terms

Fulcrum: The fixed point around which a lever pivots.
Effort Force: The force applied to implement the lever's operation.
Resistance Force: The force that the lever is working against.
Changing the distance affects the torque generated by a lever.

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Description

Test your knowledge of the different classes of levers in mechanics. This quiz covers definitions, examples, and the structure of first, second, and third class levers. Perfect for students learning about simple machines.